The growth of cellular telecommunications has placed enormous strains on the ability of the industry to satisfactorily handle the telecommunications traffic that has been generated. Consequently, users of present analog cellular telecommunications systems find that they may have to wait for a telecommunications channel to become available before they can place or receive a call. Also, a call in progress may encounter interference in the form of noise or actually over-hearing another conversation.
Sometimes, a call may be cut off while in progress if one of the parties moves to a cell that does not have an available telecommunications channel.
The problem is further aggravated by the fact that there are only a limited number of frequencies allocated for cellular telecommunications. Thus, the problem is expected to grow as the demand for cellular telecommunications expands.
The industry has developed several improved analog and digital technologies that have been successfully used to increase the number of communications channels within the limited number of available frequencies.
The most important of these technologies are time division multiple access (TDMA) and code division multiple access (CDMA).
TDMA is the technology that has the widest use. It enables a single telecommunications channel to be used for several calls. Each call is allocated a particular discrete time interval in the cycle of the telecommunications signals, thus, improving efficiency.
CDMA uses a wide band of spectrum for telecommunications signals to achieve efficiency. It differentiates between calls by imprinting a distinctive “noise” spreading signal over each telecommunications signal to differentiate it from other telecommunications signals in the cell. The receiver with computer assistance decodes the assigned “noise” signal to identify the call and then despreads the telecommunications signal.
“Frequency hopping” is a form of CDMA @hat spreads a call over a series of frequencies. It uses a code to identify the sequence of frequencies that are being used.
Additionally, work has been done with respect to developing systems which can identify weak signals emanating from a cell and segregating those signals from other signals emanating from the same cell so that when combined with a digital multiple access technique such as CDMA, the number of available telecommunications channels is dramatically increased.
Attempts to increase the availability of telecommunications channels have also included attempts to make the cells smaller and to reduce the power requirements necessary for communicating with a base station. This follows from the fact that a weak signal has a reduced ability to propagate. Thus, since its strength rapidly dissipates, the same frequency can be used in a nearby non-contiguous cell.
However, to provide the requisite number of cells that would be necessary to support a high volume of telecommunications, there would have to be an enormous number of base stations. Some experts estimate that at least 100,000 cells would be necessary simply to cover major metropolitan areas in the United States. Each cell would require its own stationary antenna tower.
In addition, an enormously complex computer system would be required in order to deal with the hand-offs which would be necessary as the cellular telephones moved from cell to cell and to manage the reuse of the frequencies assigned to particular calls.
It is not certain that the problem can be solved with a ground based system at a reasonable cost and in a reasonable period. Thus, while the typical limitations associated with such systems such as line of sight, shadowing due to signal reflection, attenuation and horizon limitations, are eliminated by reducing the size and increasing the number of cells, geographic, political, environmental and social factors may prohibit the placing of antenna towers in certain locations thereby making it not possible for cells of a suitable size to be achieved in those locations.
A satellite system where each of the satellites functions as a base station node and contributes to the creation of a cellular network avoids these problems. However, in such a system relatively powerful transmitters are required because the satellites typically orbit at about 22,500 miles above the earth. Further, unless they are geosynchronous, a means must be provided for handing off signals from one satellite to another as they pass a given point over the earth. Further, as with terrestrial nodes, a hand off means is needed as a caller moves between cells.
Additionally, satellite systems suffer from the enormous cost in connection with launching, and the virtual impossibility of repair.
Accordingly, with the foregoing in mind, the present invention relates to a wireless telecommunications network system comprising a plurality of telecommunications nodes that are located in a suborbital plane. Each of the nodes comprises means for sending and receiving broadband digital radio telecommunications signals over a wireless telecommunications channel. The telecommunications signals are modulated by code division multiple access spread spectrum technology.
The means for sending and receiving wireless, digital telecommunications signals include a plurality of antennae that are operative to receive relatively weak telecommunications signals from a source. Means are provided for decoding the telecommunications signals received by each of said antennae so that the node can identify the source, and the antenna and decoding means are operative to increase the sensitivity of the node so that it can detect and receive relatively weak telecommunications signals, so that maximum utilization of the spectrum is made available for use by the telecommunications signals without interference.
An exemplary embodiment of the invention includes a cellular-type wireless communications system including: (i) a wireless switching center connected to a telephone network; (ii) a plurality of airborne base stations each associated with a cell corresponding to a specific geographic area, each of said plurality of airborne base stations operable to directly transmit and receive communication signals to/from individual subscriber terminals within the associated cell and to/from said wireless switching center to enable communication sessions to be maintained, through the telephone network, between individual subscriber terminals and other telecommunication terminals; and (iii) at least one of said plurality of airborne base stations having at least one antenna for communicating with said wireless switching center and with individual subscriber terminals in a specific geographic region, said plurality of airborne base stations comprising at least a first airborne base station supported by a first aircraft above the geographic region and a second airborne base station supported by a second aircraft. The first airborne base station may be operative to hand off communication sessions with subscriber terminals to the second airborne base station, for example, in a manner consistent with a CDMA technology associated handoff, with the wireless switching center coordinating handoffs between the first and second airborne base stations.
An exemplary embodiment of the present invention may also include an energy storage system and a solar panel. The energy storage system and said solar panel may be operable to power the propulsion system, e.g., at night.
An exemplary embodiment of the present invention may also include a means for detecting drift of said nodes and/or airborne base stations and/or relay stations in the sub-orbital plane. Drifting of relay stations from their pre-determined locations will be detected by the tracking stations. The tracking stations will then energize thrust members on the relay stations to return them to their pre-determined locations.
An exemplary method for wireless communications in a geographic area according to the present invention includes: (i) positioning a mobile switching center at a location to facilitate communication in the geographic area, said mobile switching center switching calls between ones of a plurality of airborne base stations and a telephone network; (ii) positioning and maintaining a plurality of airborne platforms above the geographic area; (iii) supporting said plurality of airborne base stations having at least one antenna on said respective plurality of airborne platforms for directly transmitting/receiving communication signals with a plurality of individual mobile subscriber terminals on the ground in said geographic area and with said mobile switching center, to enable communication sessions to be maintained, through the telephone network, between individual subscriber terminals and other telecommunication terminals; and (iv) handing off communication sessions of subscriber terminals from one of said plurality of airborne base stations to at least one other of said plurality of airborne base stations.
In an exemplary embodiment, the platform may be positioned at a location to minimize interference with transient airplanes.